Multilayered air-fuel ratio sensing element

A multilayered air-fuel ratio sensing element has a zirconic solid electrolytic body and a heat-generating portion including an alumina substrate located adjacent to the zirconic solid electrolytic body. The zirconic solid electrolytic body is made of a partially stabilized zirconia containing 5.about.7 mol % yttria and having a mixed phase structure including a cubic phase, a monoclinic phase and a tetragonal phase. The zirconic solid electrolytic body has a relative density of 94.about.100% with a mean sintered grain size R.sub.ZR of 0.5.about.3.0 .mu.m. The alumina substrate has a relative density of 95.about.100% with a mean sintered grain size R.sub.AL of 0.5.about.4.0 .mu.m. And, the partially stabilized zirconia has an M/C ratio in a range from 0.05 to 0.25.